In an automotive fuel system, fuel is pumped from a tank through a fuel rail into an injector. The pressure of the fuel delivered to the injector is controlled to allow a desired quantity of fuel to pass through the injectors into the cylinders of the engine. Pressure regulators are incorporated in the fuel rail to provide pressure control. Excess fuel that is pumped from the tank through a fuel rail is returned to the tank through a return line.
Conventional pressure regulators used in fuel systems include either a spring loaded diaphragm or a steel ball with a leaf spring that is balanced against fluid pressure. These devices control absolute pressure in the fuel system and have the tendency to become unstable in designs that require its location directly on or near a fuel pump. This is undesirable because the pressure in the fuel system should remain as constant as possible to minimize internal losses and maximize engine power and fuel consumption. In addition to having the propensity to become unstable, pressure regulators are typically very noisy under these design conditions due to their conventional designs.